How technicly minded are you? I tend to 'spring clean' my pc and do a complete reformat every 6 months or so just to get rid of all the crap that builds up.
Isn't the answer a seperate hdd or partition for the OS and one for the data, then its simply a matter of using a ghosting program for the OS partition and restoring it every 6-12 months?
I could do, but you would still have to update the os anyway for windows updates and stuff. I know you can do something called short stripping where only the outside of the platter gets used and it goes faster but you loose 90% of the capacity and i'm not sure howto do it.